docs: update README to reflect deprecation

Faretheewell, Flex Layout.

README.md

@@ -4,6 +4,9 @@
 [![Build status](https://circleci.com/gh/angular/flex-layout.svg?style=svg)](https://circleci.com/gh/angular/flex-layout)
 [![Gitter](https://badges.gitter.im/angular/flex-layout.svg)](https://gitter.im/angular/flex-layout)
 
+**NOTE: The Angular team no longer publishes new releases of this project. Please review [this blog post](https://blog.angular.io/modern-css-in-angular-layouts-4a259dca9127) 
+for alternatives, and [this article](https://medium.com/@caerus.karu/farewell-flex-layout-aaa567023769) for the explanation and next steps.**
+
 Angular Flex Layout provides a sophisticated layout API using Flexbox CSS + mediaQuery.
 This module provides Angular developers with component layout features using a
 custom Layout API, mediaQuery observables, and injected DOM flexbox-2016 CSS stylings.